493
FXUS02 KWBC 212029
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
429 PM EDT THU MAY 21 2026
VALID 12Z SUN MAY 24 2026 - 12Z THU MAY 28 2026
...HEAVY RAIN AND THUNDERSTORMS EXPECTED TO CONTINUE ACROSS
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...
..OVERVIEW
A COUPLE OF SOUTHERN STREAM UPPER TROUGHS WILL PASS THROUGH THE
SOUTHWESTERN AND SOUTH-CENTRAL U.S. NEXT WEEK, PROVIDING LIFT FOR
WIDESPREAD RAIN AND THUNDERSTORMS IN A MOIST AND UNSTABLE AIRMASS.
THE HEAVIEST RAIN SHOULD GENERALLY AFFECT THE LOWER MISSISSIPPI
VALLEY AND SOUTHEAST SUNDAY-MONDAY, AND POTENTIALLY GET RENEWED IN
TEXAS AND VICINITY INTO THE WORKWEEK OVER AREAS THAT WILL ALREADY
HAVE WET ANTECEDENT CONDITIONS. AN UPPER TROUGH OVER THE GREAT
LAKES THIS WEEKEND SHOULD REACH NORTHERN NEW ENGLAND BY MONDAY
NIGHT, WITH WIDESPREAD SHOWERS FROM THE OHIO VALLEY TO THE
NORTHEAST AHEAD OF THIS FEATURE. OUT WEST, A MORE AMPLIFIED LEVEL
PATTERN STARTS TO EMERGE AS A STRONGER UPPER TROUGH LIKELY BECOMING
A CLOSED LOW ENTERS THE PACIFIC NORTHWEST AND ENVELOPS MORE OF THE
INTERMOUNTAIN WEST BY THE MIDDLE OF THE WEEK, YIELDING COOLER
TEMPERATURES AND PRECIPITATION. AN UPPER RIDGE SHOULD DEVELOP
DOWNSTREAM IN THE EAST-CENTRAL U.S., REACHING INTO THE UPPER
MIDWEST/GREAT LAKES AND BRINGING ABOVE AVERAGE TEMPERATURES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT MODEL GUIDANCE INDICATES REASONABLE AGREEMENT WITH THE
INITIAL PATTERN, INCLUDING THE TROUGH TRACKING THROUGH THE NORTHERN
TIER. THE FIRST SOUTHERN STREAM TROUGH ACROSS TEXAS SHOWS MOSTLY
GOOD CONSENSUS, ASIDE FROM THE CMC A BIT FAST/FARTHER NORTHEAST. IN
GENERAL THAT FEATURE HAS TRENDED A BIT FARTHER EAST OVER THE PAST
COUPLE DAYS, ALLOWING FOR A SHIFT EASTWARD IN THE PLACEMENT OF
HEAVIEST QPF. THE NORTHERN STREAM TROUGH WILL SHIFT ACROSS
SOUTHEASTERN CANADA MONDAY-TUESDAY WHILE THE SOUTHERN STREAM TROUGH
ERODES DURING THAT TIME.
MEANWHILE THE PRIMARY LARGER SCALE MODEL VARIATIONS ARE WITH THE
UPPER TROUGH MOVING TOWARD AND INTO THE NORTHWEST EARLY TO MID-NEXT
WEEK. THE LAST FEW MODEL CYCLES HAVE SHOWN A MARKED DIFFERENCE
BETWEEN THE GFS/GEFS BEING WEAKER WITH THE TROUGH AND MOVING IT
EAST MORE QUICKLY, COMPARED TO THE OTHER DYNAMICAL AND AI
MODELS/ENSEMBLES. EVEN THE GFS-BASED AI MODELS ARE SLOWER AND MORE
CLOSED OFF THAN THE DYNAMICAL GFS/GEFS. THIS GIVES MORE CONFIDENCE
TO ELIMINATE THE GFS AND GEFS FROM THE MODEL BLEND, ADJUSTING
TOWARD THE NON-NCEP GUIDANCE FROM THE NBM STARTING POINT AS
NECESSARY IN THE GRIDDED FORECAST AS WELL (COOLER TEMPERATURES AND
SLOWER MOVEMENT OF QPF THROUGH THE NORTHWEST).
..WEATHER/HAZARDS HIGHLIGHTS
HEAVY RAIN WILL CONTINUE TO BE A THREAT ACROSS THE SOUTH-CENTRAL
TO SOUTHEASTERN U.S. INTO SUNDAY AND MONDAY, WITH MULTIPLE
MESOSCALE CONVECTIVE SYSTEMS DEVELOPING. THESE WILL BE IN RESPONSE
TO ENHANCED ASCENT FROM A WEAK UPPER TROUGH IN THE SOUTHERN STREAM
FLOW, COUPLED WITH A WEAK FRONT IN THE REGION AND PLENTY OF
MOISTURE AND INSTABILITY. A SLIGHT RISK OF EXCESSIVE RAINFALL STILL
LOOKS REASONABLE FOR SUNDAY FROM FAR SOUTHEAST TEXAS INTO MUCH OF
LOUISIANA. FORTUNATELY THIS IS MOSTLY SHIFTED A BIT EAST OF THE
HEAVIEST RAINS DURING THE SHORT TERM FORECAST, BUT THERE MAY STILL
BE SOMEWHAT WET ANTECEDENT CONDITIONS THERE. THE SURROUNDING
MARGINAL RISK IN THE DAY 4 ERO WAS TRIMMED ON THE WESTERN SIDE AS
MODELS CONSOLIDATE TO THE EAST. THEN BY DAY 5/FRIDAY, THERE IS
LESSENING SUPPORT ALOFT FOR PARTICULARLY HEAVY RAINFALL AMOUNTS,
THOUGH WIDESPREAD RAIN AND THUNDERSTORMS COULD CONTINUE IN THE
MOIST AND UNSTABLE AIR. A MARGINAL RISK STRETCHING ACROSS MUCH OF
THE LOWER MISSISSIPPI VALLEY TO SOUTHEAST AND MID-SOUTH REMAINS IN
PLACE FOR DAY 5/MEMORIAL DAY.
MEANWHILE, THE NORTHERN STREAM TROUGH WILL PUSH THROUGH THE
NORTHEASTERN QUADRANT OF THE COUNTRY AND SPREAD RAIN THERE SUNDAY,
WITH LESSENING COVERAGE THROUGH MONDAY AND TUESDAY. CONVECTION ALSO
LOOKS TO SPARK IN THE FOUR CORNERS REGION ON MONDAY IN RESPONSE TO
THE NEXT SOUTHERN STREAM TROUGH ALOFT. THAT SYSTEM COULD RENEW
HEAVY RAIN POTENTIAL IN TEXAS AND VICINITY FOR TUESDAY AND
WEDNESDAY POTENTIALLY IN AREAS THAT WILL BE QUITE SATURATED FROM
THE NEAR TERM AND SHORT RANGE RAIN, WHICH BEARS WATCHING. SHOWERS
AND STORMS ARE POSSIBLE ACROSS THE MID-MISSISSIPPI AND OHIO VALLEYS
AS WELL.
UPPER TROUGHING MOVING INTO THE NORTHWEST EARLY NEXT WEEK AND A
FRONTAL SYSTEM AHEAD OF IT WILL ALLOW FOR INCREASED PRECIPITATION
REACHING THE PACIFIC NORTHWEST SUNDAY AND SPREADING SOUTHEAST ON
MONDAY AND INTO THE WORKWEEK. SNOW IS POSSIBLE AT THE HIGHEST
ELEVATIONS OF THE CASCADES TO ROCKIES.
COOLER THAN AVERAGE TEMPERATURES MAY PERSIST IN THE NORTHEAST AND
NORTHERN MID-ATLANTIC ON SUNDAY, BUT SHOULD SEE A GRADUAL WARM-UP
AFTER THAT. MEANWHILE THE WEST CAN EXPECT GRADUAL COOLING AS THE
WEEK PROGRESSES WITH THE TROUGH OVERHEAD. ON THE OTHER HAND, THE
UPPER RIDGE TO ITS EAST WILL ALLOW FOR WARMER THAN AVERAGE
TEMPERATURES ACROSS THE NORTH-CENTRAL U.S. THROUGH MUCH OF NEXT
WEEK.
TATE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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